In the prior art, several different apparatuses are known for the measurement of the fluorescence, turbidity, luminescence, or absorption of a liquid sample separately. Some systems are also known in which two or more of the measurements mentioned above are combined. In such a case, however, it has not heretofore been possible to achieve the quality of performance with combined measurements as is possible with an apparatus designed specifically for one function only.
In this connection, it is known in the art to make use of the internal total reflection in a cuvette. For example, DE No. 3 122 896 describes an equipment in which light beam goes horizontally through a chamber filled with liquid sample and in which absorbance is measured using total reflection. Vertical photometric measurement is shown e.g. in GB No. 1 486 210.